To provide a digital image encoder capable of enhancing the compression rate of an image without deteriorating the image quality in the JPEG 2000.

A DC level conversion section 31 applies DC level conversion to the received image data to enhance the efficiency of wavelet transform. When the image data are color image data, a color conversion section 32 applies color conversion processing to the image data. A wavelet transform section 33 applies wavelet transform processing to the image data subjected to color conversion to convert the image data into coefficients. A quantization section 34 quantizes the coefficients converted from the image data. A coefficient modeling section 35 applies coefficient modeling processing, from multi-value data into binary data, to the coefficients after the quantization for bit plane encoding, a low-order bit plane replacement section 36 replaces a low-order bit plane with '0' by a number of 0s set by a replacement amount 101, and an arithmetic encoding section 37 applies the bit plane encoding to the result.